Multiexchange impulse repeating system



Filed'Mafch e, 1943 2 Sheets-Sheet 2 INVENTOR R u, u T a m Patente dOct. 28, 1947 MULTIEXCHAN GE IMPULSE REPEATING SYSTEM George ThomasBaker, Liverpool, England, as-

signor, by mesne assignments, to Automatic Electric Laboratories, Inc.,Chicago, 111., a corporation of Delaware Application March 6, 1943,Serial No. 478,244 In Great Britain April 20, 1942 Claims. 1

The present invention concerns impulse repeating arrangements'for use inautomatic telephone or like systems and in particular in systems such asdescribed and claimed in my copending applications Nos. 478,243 and478,245, both filed March 6, 1943, the latter now being Pat. No.2,402,232, dated June 18, 1946, although it is to be understood that itis not exclusively limited to such applications.

The object of the present invention is to provide a highly efficientarrangement for impulsing between exchanges over an extended area beyondthe range to which the usual impulsing methods can operate reliably.

According to one feature of the present invention an impulse repeater isprovided for use in telephone or like systems in which a change ofcurrent in a predetermined sense in each impulse of direct current isadapted to cause the transmission of a momentary alternating currentover a junction line whereby impulses are transmitted over the junctionline having no relation to the duration of an impulse and separated byintervals corresponding to the interval between corresponding parts ofsuccessive impulses.

According to another feature of the present invention an impulserepeater is provided for use in telephone or like systems for respondingto momentary alternating currents in which each momentary alternatingcurrent is adapted to pass through a rectifier unit to operate a relaywhich in turn causes a momentary direct current impulse to betransmitted to a selector switch adapted to respond thereto.

The invention will be better understood by referring to the accompanyingdrawings which correspond to Figs. 23, 24 and 25 in my co-pendingapplication No. 478,245, mentioned above, now Patent No. 2,402,232.

Fig. 1 shows circuits of the switching arrangements for outgoingselector levels,

Fig. 2 shows basic circuits of a D. C./A. C. outgoing impulse repeaterfor inter-exchange working, while Fig. 3 shows similar circuits of arelay set for terminating the incoming end of inter-exchange junctions.I

The invention is described in connection with a battery feeding controlrelay set taken into use at the originating exchange to operate theswitches thereat, such relay group being switched out when the call isto be routed over an outgoing junction. In the following method now tobe described in connection with Fig. 1 relay contacts in the throughspeaking leads to the out- 2 going junction repeater (Fig. 2) relay setsare entirely avoided.

Fig. 1 illustrates diagrammatically two sets of contacts in the contactbank of a selector switch of the kind shown in my copending applicationSerial No. 478,242, filed March 6, 1943. The bank contacts of thisswitch are arranged in levels or rows, usually ten levels with ten setsof pairs of contacts in a level. One contact of each pair consists of atooth of a comb plate so that corresponding contact of each pair in alevel are multiplied together by 'a comb plate. The other contact ofeach pair is connected to an outgoing multiple and as shown there arethree pairs to a set, one corresponding to each speaking lead and one tothe private. The fourth pair of contacts allocated to a set is not usedin the present invention. Normally on a selector bank the comb platesrelevant to each of the various leads, say, negative, positive andprivate are all strapped together, but where, say, levels l-Q of a firstselector are to give access to the local'switching train, and wherelevel 0 is to give access to outgoing junctions the comb plate wiringmay be split so that the incoming speaking leads will connect viacontacts out and co l of a relay 0G and the control relay set describedmore particularly with reference to Fig. 6 of the above mentionedapplication No. 478,243, with the comb plates I-9, and will connectdirectly with the-comb plates of level 0.

The control relay set of the said Fig. 6 is taken into use in usualmanner and if any of the digits 1-9 are dialled, the selector train willbe set up in normal manner as described in my copending application No.478,243, but if digit 0 is dialled for the purpose of an outgoingjunction call, then the directly connected 6 level comb plates will comeinto operation a follows. When a free outgoing repeater is found (forinstance the one shown in Fig. 2), relay 0G will be operated over itsleft-hand low resistance winding from earthed contacts bb of the controlset relay BB to the idle resistance marking battery which will beconnected to the incoming P lead at the outgoing repeater, the lowresistance winding of relay OG serving as a guarding potential and alsoto operate relay 0G which thereupon at contact 093 and 094 disconnectsthe circuit to the control group. During the release of the controlgroup, which will take place at approximately '150 milli-seconds afterthe opening of the loop thereto, the subscribers loop will be extendedforward to operate the impulse accepting relay IA and in turn the guardrelay H3 in the Outgoing relay set (Fig. 2) and a guarding and holdingearth will be extended back to hold relay G on its other winding, beforerelay BB in the control group which has previously been holding it,releases. The subscriber will now be directly connected through to theoutgoing repeater which will receive the remainder of the trains ofimpulses to be dialled and which will provide the battery feed to thecalling subscriber. The selector will of course remain held over the Plead from earth at the outgoing relay set which will extend via contacts092 and through the control group to the selector primary control relay.

The above arrangement can also apply to the case where the groupselector has only one level giving access to the local switches in theexchange and the other levels all have access to outgoing repeatersleading to other exchanges the only difference being that instead of thecontrol relay set leading to the first nine levels it will only beconnected to the level leading to local switches while the other levelswill be connected direct to the incoming leads. The circuit arrangementsof Fig. 1 will equally apply to this arrangement. Similarly it ispossible to arrange for more than one level to be used for the localswitch train and more than one level to be used for connections to otherexchanges again employing the circuit arrangements of Fig. 1.

This facility, whereby levels may. be split to allow for differingcircuit operations according to the different level or levels involved,may have other applications.

Consideration will now be given to the question of inter-exchangeworking.

The impulsing improvements proposed in application No. 478,243, such asself-correcting switch magnets and speed timing impulse-respondingarrangements provide a highly efficient arrangement for the receipt ofimpulses, but it is possible that when several impulse repetitions areconcerned, no impulses at all will be received at the distant end.

So far a single exchange has been envisaged, and this exchange has beenmade such as to interwork into an existing area. In new areas a greaterflexibility is possible, and it seems desirable to provide an impulsingscheme in which the present impulse repetition method is obviated.

For this purpose it is proposed that all interexchange impulsing shouldbe of the alternating current type; holding and supervisory signals willstill be on a direct current basis as at present, but alternatingcurrent pulses, preferably of voice frequency, will be superimposed onthese to perform the actual movement of the selectors. In the case oftandem exchanges the received alternating current impulses will beconverted to direct current impulses for the purpose of setting up theselector train in the tandem exchange and thereafter the necessaryconversion unit will be cut out and the remainder of the alternatingcurrent impulse train will pass straight through to the terminatingexchange in the same manner as for speech currents, the direct currentsupervision arrangements being retained.

Referring now to the basic D. C./A. C. outgoing repeater circuit shownin Fig. 2, when this is taken into use via a switching arrangement suchas that shown in Fig. 1 relay IA operates and is followed by relay 13which at contacts lbl replaces the idle marking battery via, resistanceYX by a guarding and holding earth and at contacts [113 extends a D andI relay loop, either of normal type described in Saville PatentNo.2,218,659, is-

4 sued Oct. 22, 1940, or of the thermionic valve type described inTaylor and Baker application Ser. No. 446,900, filed June 13, 1942, nowPatent No. 2,350,652, dated June 6, 1944, over the right-hand outgoingjunction conductors to the distant office.

The initial energization of relay IA switches over contact 1112, and thesubsequent energization of rela IB prepares a charging circuit forcondenser QJ by closing contact I172. When relay IA releases responsiveto the first received impulse condenser QJ is charged via contacts M2and [b2 to earth while on the reenergization of relay IA at the end ofthe impulse relay IPU is energised for the discharge time of condenserQJ. Similarly, upon each subsequent impulse in the received traincondenser QJ is recharged and at the end of each impulse it causes relayIPU to reoperate for the discharge time of the condenser. Asa result ofthese momentary operations of relay IPU flick impulses of alternatingcurrent are extended from leads ACI and AC2 and then over contacts Ipul, I 10142 and N23 to the outgoing junction, the D and I loop eitherremaining intact, or in the case of the sensitive D and I relayarrangement described in the aforementioned application, Ser. No.446,900, new Patent No. 2,350,652, being rendered insensitive during theapplication of each pulse to line. As regards resistance YW this servesslowly to drain away any residual charge on condenser QJ when theoutgoing repeater is subsequently released at the end of the call.

At the distant end of the trunk line is an incoming relay set, shown inFig. 3, which preferably forms a part of a control relay set like thatdisclosed in Fig. 6 of my aforementioned application Serial No. 478,243.The said control relay set includes a ring cut-off relay F, a busy relayG and an idle relay H, which for convenience are shown schematically inFig. 3. Referring more particularly to the latter figure, rela 2Aoperates on seizure of the relay set by the forward extension of thedirect current loop and this at contact Zal operates relay 2B which inturn closes contact Zbl; relay 23 need not be slow-to-release sincerelay 2A is only adapted to respond to the direct current supervisoryand holding signals and does not do so to the subsequently receivedalternating current impulses. The latter are adapted to be received on arectifying unit RU which might consist of a. dry plate rectifier bridgefollowed by a small gas discharge tube in the anode circuit of whichrelay ZPU would be situated. As more fully described in theaforementioned application, Ser. No. 446,900, this gas discharge tubewould be caused to flash on the incremental front or on the 'decrementaltermination of each signal wave and would remain locked in until relayZPU had at contacts Zpul repeated 2. suitable flick direct current pulseout over the negative Wire to the subsequent switch train.

As soon as the call has been extended to the wanted subscriber the Hrelay in the control relay set will be operated if this subscriber isfound to be free, while the G relay will be operated if he is engaged asdescribed in connection with Fig, 6 of my copending application, Ser.No. 478,243. In either case the rectifying unit is disconnected byadditional contacts h or g of these relays from across the lines inreadiness for speech or tone transmission.

In the case of a tandem exchange an incoming selector will convenientlybe similar to that shown in Fig. 1 except that the dotted rectangle willin this case represent a control relay set combining the A. C. receivingarrangement RU of Fig. 3 and the normal functions of the control groupof Fig. 6 of application No. 478,243.

The received alternating current impulses will be converted to directcurrent flick impulses to actuate the tandem selector train via thecontrol relay set, while relay 0G will be operated as described inconnection with Fig. 1 to disconnect the modified control relay set whena tandem outgoing repeater is taken into use. Subsequent alternatingcurrent impulses will thereupon extend through to the outgoing repeaterin the tandem exchange, which it will be understood is identical to theoutgoing repeater in the originating exchange, shown in Fig. 2. and willpass through the Stone bridge therein comprising relay IA, the D and Irelay and condensers QG and QI-I with their respective contact settingresistances YT and YV to the distant incoming relay set at the requiredexchange or at another tandem exchange in the same manner as for speech.

Several points should be noted about this arrangement.

1. No attempt has been made to preserve any impulse ratio. The pulse ismerely a kick which triggers the later operations of the selector, andno regard is paid to the impulse break and make ratio determined by thesubscriber dial. The only use made of the dialled impulses is that theyserve to indicate the number of impulses in a train. This arises from acombination of self-correcting magnets and speed timing.

2. No difliculty is encountered with speech condensers and moreover theimpulse receiving shunt is removed before either tones or speech isrequired. This arises from the position of the bridge preceding thefirst selector.

3. The system combines easily with the long distance voice frequencysystems. When it is desired to work over a 2 V. F. or some other all A.C. system, arrangements are provided in association with lines outgoingfrom the area to transform the seizing and supervisory signals into theappropriate A. C. equivalents. The dialing and actuating pulses are sentout unchanged.

I claim:

1. In an impulse repeater, means for receiving direct current impulseseach having a make period of a certain duration and a break period of acertain duration, and means controlled by one of said periods of eachreceived impulse but not by the other period for transmitting atransitory impulse of alternating current, whereb a single impulse istransmitted for each received impulse and the duration of thetransmitted impulse is independent of the duration of either period ofthe corresponding received impulse.

2. In a telephone system having three exchanges connected in series bytrunk lines, means in the first of said exchanges for transmitting tothe second of said exchanges impulses of alternating current, a repeaterin said second exchange, a direct path through said repeater forconducting said impulses without repetition to' the third of saidexchanges, and means in said repeater for converting impulses generatedlocally in said second exchange into impulses of alternating current andtransmitting said last impulses to said third exchange.

3. In a telephone system having three exchanges connected in series bytrunk lines, means in the first of said exchanges for transmitting tothe second of said exchanges impulses of alternating current, means insaid second exchange for'receiving part of said impulses and convertingthem into corresponding impulses of direct current, and switchingapparatus in said second exchange at times controlled by the convertedimpulses to complete a direct path through said second exchange forconducting the remainder of said alternating current impulses withoutconversion to the third of said exchanges. V y

4. A telephone system as claimed in claim 3, wherein direct currentsupervisory signals are transmitted over the same interexchange trunklines as said alternating current impulses.

5. In a telephone system having three exchanges connected in series bytrunk lines, means in the first of said exchanges for transmitting tothe second of said exchanges impulses of alternating current, means insaid second exchange for receiving part of said impulses and convertingthem into corresponding impulses of direct current, a repeater in saidsecond exchange, switching apparatus in said second exchange at timescontrolled by the converted impulses to complete a direct path throughsaid repeater for conducting the remainder of said alternating currentimpulses without conversion to the third of said exchanges, and means insaid repeater for at times converting direct current impulses generatedlocally in said second exchange into corresponding impulses ofalternating current and transmitting said last impulses to said thirdexchange.

6. In a telephone system, two exchanges, a line between said exchangesover which supervisory impulses of direct current are transmitted attimes, means in one of said exchanges for receiving direct currentimpulses each having a make period of a certain duration and a breakperiod of a certain duration, means controlled by one of said periods ofeach received impulse but not by the other period for impressing uponsaid line a transitory impulse of alternating current, whereby a singleimpulse of alternating current is impressed upon said line for each ofsaid received impulses and the duration of such alternating currentimpulse is independent of the duration of either period of thecorresponding received direct current impulse.

7. In a telephone system, two exchanges, a direct current supervisorycircuit interconnecting said exchanges, a relay in one of said exchangesconnected to said circuit and controlled by direct currentimpulsesreceived thereover, means at the other of said exchanges forsuperimposing flick impulses of alternating current upon said circuit,said relay being non-responsive to said flick impulses, and other meansin said one exchange responsive to said flick impulses.

8. In a telephone system wherein calls local to an originating exchangeand calls outgoing from the originating exchange to another exchangeboth are extended under the control of impulses transmitted to theoriginating exchange from the calling subscriber's station, switchinapparatus in each of said exchanges, means in said originating exchangefor receiving said impulses, means controlled by said receiving means ona local call for converting the received impulses into correspondingflick impulses of direct current and transmitting said flick impulses tosaid switching apparatus in the originating exchange to control theextension of the call, and means controlled by said receiving means onan outgoing call for converting the received impulses into correspondingflick impulses of alternating "7 current and transmitting said lastimpulses to the switching apparatus in said other exchange to controlthe extension of the call.

9. In a telephone system having three exchanges connected in series bytrunk lines, means in the first of said exchanges for transmitting tothe second of said exchanges flick impulses of alternating current, arepeater in said second exchange, a direct path through said repeaterfor conducting said impulses without repetition to the third of saidexchanges, and means in said repeater for converting impulses generated10- cally in said second exchange into flick impulses of alternatingcurrent and transmitting said last impulses to said third exchange.

10. In a telephone system having three exchanges connected in series bytrunk lines, means in the first of said exchanges eifective whenever itis desired to extend a call to either of the other exchanges to transmitto the second of said to receive said impulses and repeat them to saidapparatus to control the completion of said call j in said secondexchange, and means for at other times conducting said impulsesdirectly, Without repetition, through said second exchange to Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,534,549 Smith Apr. 21, 19251,746,327 Beckerath Feb. 11, 1930 2,153,313 Pfannschmidt Apr. 4, 19391,908,365 Keyser May 9, 1933 2,102,137 Sperry Dec. 14, 1937 2,103,301Saunders Dec. 28, 1937 1,589,409 Miller June 22, 1926 2,133,055 HebelOct. 11, 1938

